Effect of addition of a non-equidiffusional reactant to an equidiffusional diffusion flame

A Burke–Schumann (flame-sheet) formulation is developed for diffusion flames between a fuel and oxidiser with Lewis numbers of unity, subject to addition to the fuel and/or oxidiser stream of a different reactant for which the Lewis number differs from unity. This formulation is applied to laminar counterflow diffusion-flame experiments, reported here, in which hydrogen was added to either methane–nitrogen mixtures or oxygen–nitrogen mixtures at normal atmospheric pressure, with both feed streams at normal room temperature. Experimental conditions were adjusted to fix selected values of the stoichiometric mixture fraction and the adiabatic flame temperature, and the strain rate was increased gradually, maintaining the momentum balance of the two streams, until extinction occurred. At the selected sets of values, the strain rate at extinction was measured as a function of the hydrogen concentration in the fuel or oxidiser stream. The ratio of the fraction of the oxidiser flux that consumes hydrogen to the fraction that consumes fuel was calculated from the new Burke–Schumann formulation, and it was found that, within experimental uncertainty, the ratio of the extinction strain rate with hydrogen addition to that without was the same at any given value of this oxygen flux ratio, irrespective of whether the hydrogen was added on the fuel or oxidiser side. This experimental result was also in close agreement with computational predictions employing detailed chemistry. These results imply that differences in detailed hydrogen concentration profiles within the reaction zone have little or no influence on the chemical kinetics of extinction when the stoichiometric mixture fraction, the adiabatic flame temperature, and the proportion of oxygen that consumes the added fuel are fixed. This same correspondence may be expected to apply for other fuels and additives.     

Photocatalytic performance of combustion-synthesized β and γ-Ga2O3 in the degradation of 1,4-dioxane in aqueous solution

Nanostructures of β and γ-Ga₂O₃ were prepared by the solution combustion route using urea as fuel. The synthesized nano photocatalysts were characterized by use of XRD, FT-IR, BET, TEM, TGA–DTA, DRS, and Raman spectroscopy. XRD and TEM investigations confirmed the nanostructures; particle size was in the range 3–5 nm for γ-Ga₂O₃ and 40–50 nm for β-Ga₂O₃. The specific surface area of γ-Ga₂O₃ was 91 m² g^?1 and that of β-Ga₂O₃ was 24.3 m² g^?1. The polymorphs of gallium oxide were used as photocatalysts for decomposition of 1,000 mg/l 1,4-dioxane. More than 90 % of the 1,4-dioxane could be degraded in less than 180 min by use of 10 mg/l photocatalyst + 0.5 ml H₂O₂. The efficiency of photocatalytic degradation of 1,4-dioxane by the synthesized photocatalysts was compared with that of P-25 TiO₂ and followed the order γ-Ga₂O₃ ≥ β-Ga₂O₃ > P-25 TiO₂. The degradation was found to follow pseudo first-order kinetics.     

Thermodynamics of binding of 2-methoxy-3-isopropylpyrazine and 2-methoxy-3-isobutylpyrazine to the major urinary protein

In the present study we examine the thermodynamics of binding of two related pyrazine-derived ligands to the major urinary protein, MUP-I, using a combination of isothermal titration calorimetry (ITC), X-ray crystallography, and NMR backbone (15)N and methyl side-chain (2)H relaxation measurements. Global thermodynamics data derived from ITC indicate that binding is driven by favorable enthalpic contributions, rather than the classical entropy-driven hydrophobic effect. Unfavorable entropic contributions from the protein backbone and side-chain residues in the vicinity of the binding pocket are partially offset by favorable entropic contributions at adjacent positions, suggesting a "conformational relay" mechanism whereby increased rigidity of residues on ligand binding are accompanied by increased conformational freedom of side chains in adjacent positions. The principal driving force governing ligand affinity and specificity can be attributed to solvent-driven enthalpic effects from desolvation of the protein binding pocket.     

Synthesis,Structure and Magnetic Phase Transitions of the Manganese Succinate Hybrid Framework,Mn(C4H4O4)

An anhydrous manganese succinate, Mn(C₄H₄O₄), has been synthesised hydrothermally and studied by single‐crystal X‐ray diffraction. It adopts a succinate pillared structure in which layers of corner‐sharing MnO₆ octahedra alternate with sheets that contain chains of edge‐sharing octahedra. This unique 3D framework structure contains highly distorted MnO₆ octahedra, which are made possible by the lack of ligand field stabilisation energy for the high‐spin Mn²⁺ ion. Attempts to dope the structure with other divalent transition‐metal ions were accordingly unsuccessful. Magnetic susceptibility and heat capacity measurements indicate that Mn(C₄H₄O₄) undergoes antiferromagnetic ordering below 12 K, with a second antiferromagnetic transition at approximately 6 K. These two antiferromagnetic phases undergo further transitions in applied fields, underlining the subtle magnetic behaviour that is possible in inorganic–organic frameworks of this structural complexity.     

Characterization of Thermostable Serine Alkaline Protease from an Alkaliphilic Strain Bacillus pumilus MCAS8 and Its Applications

This study describes the characterization and optimization of medium components for an extracellular detergent, surfactant, organic solvent and thermostable serine alkaline protease produced by alkaliphilic Bacillus pumilus MCAS8 strain isolated from Pulicat lake sediments, Tamil Nadu, India. The strain yielded maximum protease (2,214?U/ml) under optimized conditions: carbon source, citric acid??1.5?% (w/w); inducer, soyabean meal??2?% (w/w); pH?11.0; shaking condition 37?°C for 48?h. The enzyme had pH and temperature optima of 9.0 and 60?°C, respectively. The enzyme displayed the molecular mass of 36?kDa in sodium dodecyl sulphate?Cpolyacrylamide gel electrophoresis study and exhibited activity at a wide range of pH (6.0?C11.0) and thermostability (20?C70?°C). More than 70?% residual activity was observed when the enzyme was incubated with dithiothreitol, ethylenediaminetetraacetic acid, ethylene glycol tetraacetic acid and H₂O₂ for 30?min. The protease activity was also enhanced by divalent cations such as Ba²⁺, Ca²⁺ and Mg²⁺ and was strongly inhibited by Fe²⁺, Zn²⁺, Sr²⁺, Hg²⁺ and urea. The enzyme retained more than 50?% of its initial activity after pre-incubation for 1?h in the presence of 5?% (v/v) organic solvents such as dimethyl sulphoxide and acetone. The protease could hydrolyse various native proteinaceous substrates (1?%?w/v) such as bovine serum albumin, casein, skim milk, gelatine, azocasein and haemoglobin. Wash performance analysis of enzyme revealed that it could effectively remove blood stains from the cotton fabric, thus making it suitable to use as an effective detergent additive. The protease enzyme also exhibited promising result in the dehairing of goat skin. The potency of the eco-friendly enzyme without using any chemicals against washing and dehairing showed that the enzyme could be used for various industrial applications.     

Hydrolysis and amine-capping in a glycol solvent as a route to soluble maghemite gamma-Fe2O3 nanoparticles

The preparation of capped metal oxide nanoparticles through the hydrolysis of metal salts is made arduous by the difficulty of dissolving long organic chain capping agents in water; by performing the reaction in propylene glycol under reflux, instead of water, we are able to hydrolyse FeCl3 in the presence of n-octylamine to obtain (repeatedly) soluble, monodisperse approximately 5 nm gamma-Fe2O3 particles that display a tendency to aggregate into superlattices.     

Novel synthesis of benzo[b]carbazoles

A new method was adopted for the synthesis of benzo[b]carbazoles by Claisen condensation followed by Fischer indole cyclization. Newly synthesized benzo[b]carbazoles were treated with ethanol amine in the presence of polyphosphoric acid which leads to the formation of pyrazino carbazoles. All the synthesized compounds were characterized by all spectral means.     

Impact of Targeted Specific Antibiotic Delivery for Gut Microbiota Modulation on High-Fructose-Fed Rats

The objective of present investigation was to study the effect of gut microbiota alteration by oral administration of targeted delivery of pH sensitive cefdinir microspheres to high-fructose-fed (HFD) rats. Rats were fed with a high-fructose diet with or without cefdinir microsphere administration for 30 days. The fecal microbiota community, oral glucose tolerance, the markers of liver injury, plasma and hepatic lipids profile, and histological evaluation were investigated. The levels of blood glucose, liver injury markers, lipid profile in plasma and liver, and fat tissue were significantly increased in high-fructose-fed rats. However, after pH-sensitive cefdinir microsphere administration, the elevation of these parameters was significantly suppressed. Cef EL significantly lowered the increased AST (p?<?0.05) and ALT (p?<?0.001) levels in HFD group. There is a significant lower (p?<?0.01) AUC_glucose level in Cef EL group than HFD group The histological changes in the liver and the small and large intestines were more profound in HFD group as compared to cefdinir-treated HFD and control groups. Feeding of cefdinir microsphere sustained lactobacilli and bifidobacteria and significantly decreased (p?<?0.05) the number of Enterobacteriaceae induced by HFD. Experimental evidences demonstrated that the effectiveness of pH-specific cefdinir microsphere on reducing insulin resistance and development of metabolic changes in high-fructose-fed rats and suggested that it may be a promising therapeutic agent in treating type 2 diabetes. Intestinal-targeted antibiotic delivery needs to be further explored for its therapeutic applications.